Dennis Robertson
Crestline, California
--- In californiadisasters@yahoogroups.com, Kim Noyes <kimnoyes@...> wrote:
>
> Super Soggy December
>
> by Dave Bruno ~ NWS Los Angeles/Oxnard
>
> Thanks in large part to a huge upper level low pressure system that brought
> rain to the region from the 17th through the 22nd, December 2010 will go
> down in the record books as one of the wettest, and in many cases the
> wettest, Decembers in history across southwestern California. Most of
> southwestern California received between 3 and 6 times the normal rainfall
> for the month, or 300 to 600 percent of normal.
>
> The first few days in December 2010 were generally mild and dry across the
> region. A storm system moved into central California on the 5th. Its
> associated front brought rain to the region on the 5th into the early
> morning hours of the 6th. Rainfall totals generally averaged one third of an
> inch to three quarters of an inch across the region. Gusty south winds
> affected the mountains, with wind gusts of 40 to 50 mph common from the
> afternoon of the 5th through the early morning hours on the 6th.
> Dry weather returned on the 6th and continued through the middle of the
> month.
>
> A dramatic change in the weather pattern began after the 16th. A large upper
> level low pres-sure system moved into the northeastern Pacific, well off the
> coast of the Pacific Northwest on the 17th, then lingered there through the
> 21st. The circulation around the southern side of this upper low pushed very
> moist air with a subtropical con-nection into the region. This ribbon of
> moisture remained focused across southern California from the 17th through
> the 21st, bringing almost continuous rain to the region during that time.
> Several impulses rippling through the moist subtropical flow caused periods
> of heavy rain at times. On the 21st, the upper low began to shift eastward.
> Its associated strong frontal system moved across southwestern California
> late on the 21st through the 22nd, putting an exclamation point on what was
> a very wet week.
>
> Many daily rainfall records were set across the region from the 17th through
> the 22nd. Some noteworthy records include the following:
>
> On the 18th, daily rainfall records included 3.19 inches at Santa Maria
> airport and 2.80 at San-ta Barbara airport, both of which also set new
> rec-ords for any day during any month of December.
> On the 19th, daily rainfall records included 2.80 inches at downtown Los
> Angeles, which was its 8th wettest December day ever. At Santa Barba-ra
> airport, the total of 2.79 inches set a new daily record. It was also its
> 2nd wettest December day ever, the wettest having been set the previous day.
> The daily total of 2.07 inches at Long Beach air-port set a new record for
> the day, and was its 3rd wettest December day ever. At Los Angeles air-port,
> the daily total of 2.23 inches set a new daily record, and was the 4th
> wettest December day ever.
> On the 20th, a new daily rainfall record was set at Long Beach airport with
> 2.03 inches, its 4th wettest December day ever.
>
> The week long siege of rain brought periods of flooding to the region, along
> with some mud and debris flows and rock slides, the most serious of which
> occurred on the 22nd. Significant flooding of the transition road between
> interstate 10 and high-way 57 was reported during the early morning of the
> 22nd, with a large amount of water in lanes and mud coming down from the
> hill sides. A small mountain side collapsed onto Little Tujunga canyon road
> at Sand Canyon Highway during the late morning hours, and rocks and debris
> covered all lanes at one point. During the afternoon hours of the 22nd, all
> lanes of Big Rock Creek Road in the Antelope Valley were covered by flooding
> and debris, and mud and heavy flooding was reported on an onramp to the 10
> Freeway east of downtown Los Angeles. Three cars were trapped in flood
> waters on Avenue H east of Lancaster during the early afternoon hours, and
> five people had to be rescued. A funnel cloud was reported near the San
> Pedro area at 240 pm on the 22nd.
>
> Rainfall totals for the week long storm were impressive, averaging 5 to 10
> inches in coastal and valley areas...and 10 to 18 inches in the foothills
> and mountains, with local totals as high as 24 inch-es in the San Gabriel
> Mountains and the mountains of western Ventura County.
>
> After a couple of dry days, another front swept through the region late on
> the 25th and into the 26th. The front brought rainfall totals of one half
> inch to one inch in most areas with locally higher totals, especially in the
> foothills.
>
> The final weather system of the month swept through the region late on the
> 28th and 29th. Rainfall for this system ranged from 0.75 inches to 1.50
> inches north of Point Conception, and between 0.50 and 1.00 inches south of
> Point Conception, with locally higher amounts in the foothills.
>
> In downtown Los Angeles, the 10.23 inches of rainfall received in December
> was the second most in any December since records began in 1877. It also
> made December 2010 the 14th wettest of any month in history at the site.
> Rain-fall in December 2010 was equal to nearly 70% (67.5%) of the entire
> seasonal normal for downtown Los Angeles, which is 15.14 inches.
>
> <SNIP>
>
> View entire article here:
> http://www.wrh.noaa.gov/lox/spotter/documents/Newsletter_april2011.pdf
>
> --
> Check out http://groups.yahoo.com/group/californiadisasters/
> Read our blog at http://eclecticarcania.blogspot.com/
> Visit me on Facebook at http://www.facebook.com/derkimster
>
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